Article for lunch?
Does lunch have an -en or an -ett?
Yes, it's en mat (and hence maten = the food). But you wouldn't often use en mat, you would say en maträtt (a dish). If you use en mat, it sounds a bit like a lazy contraction of maträtt.
You can check the grammatical gender of any Swedish word here: http://www.svenskaakademien.se/svenska_spraket/svenska_akademiens_ordlista/saol_13_pa_natet/ordlista. Just type the word or the beginning of the word in the box, and it will show you that page of the dictionary.